Foot pounds of recoil is not near as important as recoil velocity. For instance if you have a 6 lb gun & a 9 lb gun recoiling at the same velocity the 9 pounder will have 50% more foot pounds, but will not affect you 50% worse.
If on the other hand you increase the recoil velocity of that 6 lb gun to give equal foot pounds as the 9 pounder it will kick the Snot out of you. If you take the total weight of everything that goes out of the barrel, multiply it by the velocity & then divide by the weight of the gun this will give you its "Approximate" recoil velocity. The reason it is approximate is that once the wads clear the muzzle the expanding gases escape at a higher velocity thus that portion is not identical to the shot & wads. The suggestion has been made to use 1.25 times the powder charge for an even closer approximation, thus if you were loading a 20 gr charge enter 25 instead. Keep in mind all weights "Must" use the same units. Matters not if you convert to grains, ounces or pounds, so long as all are the same.
